Profiled tool and apparatus for the production of paper making pulp



Oct. 20, 1964 D ATAcK T 3,153,511

PROFILED TOOL AND APPARATUS FOR THE PRODUCTION OF PAPER MAKING PULP Filed Aug. 25. 1961 4 Sheets-Sheet 1 0d. 20, 1964 D ATACK ETAL 3,153,511

E PRODUCTION PROFILED TOOL AND APPARATUS FOR TH OF PAPER MAKING PULP 4 Sheets-Sheet 2 Filed Aug. 25 1961 I71Ye7v75 Dauy/as 4722414 WO. Ma

Oct. 20, 1964 D. ATACK ETAL 3,153,511

PROFILED TOOL AND APPARATUS FOR THE PRODUCTION OF PAPER MAKING PULP Filed Aug. 23, 1961 4 Sheets-Sheet 3 &

U k 1 x 72 3, 92 94 74a 1 7401 1 L, A Jim e715;

74 Gul /a5 Ame v W- D May J 4 PM AMA M? 72w Oct. 20, 1964 D. ATACK ETAL 3,153,511

PROFILED TOOL AND APPARATUS FOR THE PRODUCTION OF PAPER MAKING PULP 4 Sheets-Sheet 4 Filed Aug. 23. 1961 SEES:

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M M w Maw A mhmwiv 44 A United States Patent The Pulp & Paper Research Institute of Canada, Man

treal, Quebec, Canada Filed-Aug. 23, I961, Ser. No. 133,443 Ciaims priority, applicationCanada June 23, 1961 24 Claims. (6!.241-277) This invention relates to an apparatus for the production of paper making pulp from wood and to a pulping tool used in such apparatus.

The standard commercial apparatus for the direct production of paper making pulp from logs or other large fragments of wood has been the abrasive pulpstone. The pulpstone suffers, however, from several disadvantages. A pulpstone has an initial conditioning period during which poor quality pulp is produced due to the cutting action of the sharp edges of its abrasive particles. Production from a pulpstone decreases significantly after a period of normal operation due to dulling of the surface. The pulpstone then has to be crush dressed with a metal burring tool. In this sharpening process a quantity of abrasive is removed from the surface and part of the remaining abrasive in the surfaceis loosened. Even if reasonable precautions are taken to separate the abrasive removed in sharpening, much of the abrasive loosened from the stone surface finds its way into the pit pulp and from thence into the paper machine. The abrasive worn off during the conditioning period also goes to the paper machine. The presence of the abrasive in the pulp in the paper machine has a detrimental effect on the life of the wires of the paper machine. Metal grinding wheels have previouslybeen proposed and these have cutting elements which have been variously described as scraping blades, roughened surfaces, grating, rasping or filing surfaces, picked surfaces, rough dressed corrugated surfaces, surfaces containing cutting teeth or knives. When such surfaces rub against wood they cut or gouge small fragments from the wood. None of these have produced a satisfactory pulp as evidenced by the fact that such metal grinding wheels have not replaced pulp stones in spite of the disadvantages of pulp stones.

It has been discovered in. accordance with this invention that a satisfactory pulp can be produced using a pulping tool having protuberances of a particular profile projecting from a surface of the body of the pulping tool. More particularly the protuberances have convex crowns which are arcuately shaped in the general direction of the intended relative movement between the grinding tool and the wood. Thus the crowns of the protuberances may be shaped in section in planes including the direction of intended relative movement between the protuberances and the wood and perpendicular to said surface sub stantially in the form of segments of conic sections. The crowns of the protuberances may be approximately hernispheres or hemicylinders. The protuberances are substantially free from cutting surfaces. The protuberances are adapted to create localized high intensity stresses in the subsurface of the wood to give aloosening of the wood structure and to cause the detachment of fibers from the wood. The height of the protuberances above the surface of the body of the tool is suflicient to provide such stresses without an excessive load being borne by pulp in the spaces between the protuberances and the height of the protuberances is insutlicient to cause burning of thewood. The spacing of the protuberances is sufiicient to give such stresses but insufficient to give gross breakdown of the ice wood structure and the arrangement of spacing of the protuberances transverse to the direction of movement is such as to avoid grooving .by providing protuberances overlapping each space in the direction of movement.

In the drawings which illustrate the preferred embodiments of this invention;

FIGURE 1 is a sectional elevation view of an apparatus in accordance with this invention;

FIGURE 2 is a sectional elevation view on the line 2-2 of FIGURE 1.

FIGURE 3 is a detail View of part of FIGURE 1 illustrating the pulping zone;

FIGURE 4 is a detail view of one of the sectors shown in FIGURES l to 3;

FIGURE 5 is a detail section view of the surface of the sector shown in-FIGURE 4;

FIGURE' is a perspective view of the pulping wheel shown in FIGURES l to 3 showing the pulping wheel partially disassembled;

FIGURE 7is a perspective view of a retainer ring adapted to be assembled with the pulping wheel of FIG- URE 6;

FIGURE 8is a detail view of one of the spacers between the sectors shown in FIGURE 4;

FIGURE 9 is a sectional perspective view of part of a pulping wheel showing the assembly of the retainer ring in FIGURE 7 with the sectors in FIGURE 4 and the spacers in FIGURE 8;

FIGURE 10 illustrates an alternative embodiment of- FIGURE 13 is an elevation view of a further alterna-- tive embodiment showing a pulping wheel with a reciprocating pattern;

FIGURE 14 is a plan view of the surface of a pulping tool suitabie for use in the embodiments shown in FIG- URE l or 10;

FIGURE 15 is a sectional view on the line 15-15 of FIGURE 14;

FIGURE 16 is a plan view of the surface of a sector of a pulping tool.

Referring now to FIGURES 1 and 2 of the drawings, the pulping apparatus illustrated comprises a housing having a cylindrical side wall 24 a front wall 21 and a back wall 22. A pulping wheel 23 is disposed within the housing and is mounted on shaft 24 which is driven .by motor 25. Side wall 20 is aper-tured as indicated at 26 to receive wood 27 and is provided with webs 28. Wood .27 is slidable in a guide pocket 30 so that the wood bears against the peripheral surface of pulping wheel 23. The grain of the wood should run transverse to the direction of intended relative movement. Load is applied to wood 27 by means of weights 31 mounted on a support 32 which is connected by rod 33 to a piston-like member 29 which bears against wood 27. Rod 33 is guided by loading platform 34 which loading platform also supports guide pocket 39. Supporting members 35 and 36 are provided for loading platform 34. Water is supplied for pulping purposes by spray 37 which is mounted in back wall 22 and supplied with water through pipe 39. Valve 41 controls the flow through pipe 3%. The pulp is removed from the housing by means of a discharge outlet 43 which has a control gate 44 which slides in guides 45. Control gates 44 of various heights can be substituted. Bolts 46 secure front wall 21 to side wall 20.

FIGURE 3 is a detailed view of the peripheral pulping which have a pulping surface spaced by spacers 51. The spacers 51 provided drainage channels for the retention of pulp formed on the surface of sectors 5t). The upper surfaces of spacers 51 is below that of the sectors St).

An individual sector is illustrated in FIGURE 4 which shows the pulping surface 52 of sector 5-9. Pulping surface 52 has numerous hemicylindrically shaped protuberances such as 53 spaced from each other both in the direction of movement of the sector and transverse to such direction of movement and with the spaces transverse to such direction of movement staggered to avoid the grooving which would occur if there were spaces aligned in the direction of movement. FiGURE 5 illustrates the hemicylindrically shaped protuberances in section in greater detail and it will be noted that the crown 54 of each protuberance is shaped substantially semicircularly in the direction of travel of the sectors and that the crown 54 is supported by root portion 54a. The protuberances have a height h and a radius of curvature r. The centreto-centre spacing of the protuberance is indicated at s. The width of the crown of a protuberance is indicated at a and the length is l. The appropriate ranges of dimensions will be discussed below. The end of each hernicylinder is substantially rounded ofi as indicated at 55 to avoid the provision of cutting surfaces.

At the base of each sector there is a mounting portion 55 defined by undercutting at 56 and 57. The mounting portions 55 of the sectors enable the sectors to be firmly secured to the body of pulping wheel 23. Pulping wheel 23 is shown partly disassembled in FlGURE 6. The pulping wheel 23 comprises a disc 68 having an undercut portion 61 at one peripheral edge and a seat portion 62 at the other peripheral edge to receive retainer ring 63. Retainer ring 63 is shown in FIGURE 7. The undercut portion 61 of the pulping wheel together with a corresponding undercut portion 64 of retainer ring 63 mate with the undercut portions 56 and 5'7 of sectors 50 to provide a dovetail mounting. Similarly undercut portions 65 and 66 illustrated in FIGURE 8 at the base of spacer 51 are engaged. The manner in which the spacers 51, the sectors 5%, disc 66 and retainer ring 63 are assembled is further illustrated in FTGURE 9 which shows retainer ring 63 held in position by bolts 67 which engage holes 63 in retainer ring 63 and holes 69 in disc 6h.

In the alternative embodiment shown in FIGURE a tool 79 has pulping elements 71 separated by spaces '72. Each pulping element 71 has on its surface protuberances generally similar to those of sector 5t? but preferably differing in the manner which will be discussed below. The wood being ground is indicated at 73 and is supported on table 7d which has stop blocks 74a to prevent the wood from moving during pulping. A flexible tube 75 is connected to tool 7% to supply water to the pulping zone. Load is applied by weight 76. Pulping tool 7% is caused to reciprocate by means of motor '77 which drives a shaft 78 upon which is mounted a cam 79. Cam follower 59 is mounted on rod 82. Rod 82 is guided by support members 8i and 83. Rod 82 has a head formed to provide a vertical slot defined by webs 35 and dd. A connecting link 84 is attached at one end to tool "it? and at its other end is supplied with rollers 87 and 88 which engage Web 85 to provide a coupling while permitting connecting link 84 to descend as wood 73 wears away. A return spring 89 keeps cam follower 3% bearing on cam '79.

FIGURE 11 shows the pulping zone of FIGURE 10 in detail and illustrates also the feed apertures 9% which supply water from'tube 75 to channel 72 to lubricate the pulping zone. As illustrated in FlGURE ll the reciprocating motion causes the fibre to form rolls such as roll 91 which are discharged from and re-enter the interface 92 between the pulping elements Ill and the wood as illustrated by roll 93 until they are large enough to be trapped in channel 72 as shown byroll 91. With each full reciprocating stroke rolls of fibres are discharged as indicated at d4.

FIGURE 12 illustrates in cross section a suitable profile for pulping elements 71. The protuberances 95 have a centre-to-centre spacing S in the direction of reciprocation. Their crowns have a radius R and a width W. They have supporting roots 96 subtending an angle a and these supporting roots have a width W In the alternative embodiment shown in FIGURE 13 grinding wheel lltltl is mounted on shaft lltll which is driven by motor Th2. The wood being ground is shown at 163 and suitable sprays are provided to lubricate the pulping zone as illustrated at 104. Hemicylindrical protuberances 1435 are arranged in a sinuous pattern around the peripheral surface of wheel 10% so that rotation of the wheel causes the pattern of the protuberances to reciprocate relatively to wood N3 in the direction indicated by the arrows.

FIGURES 14 and 15 indicate a profile alternative to that shown in FIGURES 5 and 12 in which the tool lit? has hemispherical protuberances 111 projecting from its surface.

FEGURE 16 is a plan view of a sector 12) showing an alternative profile having advantages from the point of view of machining. Protuberances 121 are machined extending transverse to the intended direction of travel (indicated by the arrow) the full width of the sector. Channels 122 are then machined through protuberances 121 and oblique to the intended direction of travel.

As previously indicated the profiled surfaces provided by the protrusions shown in FIGURES 5, 12, 14, 15 and 16 have no sharp edges. When wood is pressed against this profiled surface noncutting or gouging of the wood occurs. Instead, owing to the cyclic deforming action of the profile on the wood, and the localized stresses microfracture occurs in the immediate sub-surface of the wood loosening the wood structure. The actual pulp removal from the loosened wood structure is believed to be initiated by the action of a few pulp fibres which become completely detached from the wood surface, owing to the repeated cyclic compression and recovery of the wood under the profile. The detached fibres are carried into the pulping zone. These detached fibres in their subsequent passage through the pulping zone react upon the loosened wood structure and remove partially loosened fibres by entangling with them and rolling them out. This removal of fibres is auto accelerative.

The crowns of the protuberances should be arcuate in the direction of relative movement with respect to the wood and preferably are substantially semicircular. In the following discussion the protuberances will be discussed in terms of those having a semicircular shape for convenience and clarity, though it will be appreciated that other arcuate shapes can be used. Considering now the dimensions in a direction transverse to that of the relative movement the crowns of the protuberances may range from approximate hemicylinders to hemispheres. In this connection it is noted that a hemisphere may be regarded as being the limiting case of a hernicylinder in which there is a length to width ratio of unity. Where the protuberances are hemicylinders the ends are rounded off to approximate the quadrant of a sphere thereby avoiding cutting edges.

' The length to width ratio of the hemicylinders may be varied quite widely. In FIGURE 5 the length is designated l and the width :2. It has, however, been found that where the relative movement between the Wood and the protuberances is unidirectional, as in FIGURE 1, the results improve as the length to width ratio of the hemicylinders approaches unity. It is therefore preferred for unidirectional movement that the length to width ratio be from 20:1 to 1:1. Where, however, there is reciprocating movement hernicylinders are preferable to hemispheres and the length to width ratio of the hemicylinders can be large, for example they may extend the width of the tool provided that other dimensions are chosen so as to obtain the necessary stress intensity.

The radius of the crowns of the protuberances should preferably be in the range 0.002 to 0.006 inch as this provides a stress intensity suitable for providing the desired loosening action without giving a cutting etfect. The radius is shown at r in FIGURE 5 and R in FIG- URE 12. The height ofthe protuberances above the surface of the tool designated h in FIGURE 5 should be in the range 0.002 to 0.010 inch for best performance. If the height is insutficient it is difi'icult or impossible to. provide the desired stress intensity because the pulp fills the interprotuberance spaces as it is formed to an extent such that the pulp takes a large proportion of the load. If on the other hand the height of the protuberance's is too great it has been found that burning occurs. In addition the height of the protuberances affects the ability of the pulp to remove additional fibers. This wasv demonstrated by varying the height of the protuberance above its surroundings. When this height exceeded 0.010 inch the rate of pulp removal decreased very rapidly and at about 0.014 inch the rate was substantially zero and the tool burned the wood surface. At heights less than 0.004 inch the rate of pulp production again fell due to the excessive load borne by the pulp in the zone. Under such loads the pulp is broken down excessively and as the height is reduced the efiect is to produce a finer pulp (lower freeness) at a decreased rate. It is believed that in this case since a larger part of. the load is borne by the pulp the stress intensity in the wood, above the protuberances required for loosening is not attained. The interprotuberance spacing both in the direction of movement and transverse thereto must be sufiicient to give the desired stresses but insuificient to give gross breakdown of the wood structure. The interprotuberance spacing in the direction of movement is particularly important in this respect. This spacing is designated s in FIGURE 5 and S in FIGURE 12. The best interprotuberance spacing depends on the type of relative movement. Where there is reciprocating movement the eificiency of pulp production is higher than if unidirectional relative movement is employed and the pulp quality is better. It has been found that a closer interprotuberance spacing in the direction of movement may be employed at lower magnitudes of the normal loading to produce pulps of news grade groundwood quality as compared with the interprotuberance spacing Where there is unidirectional movement. For reciprocating movement the interprotuberance spacing is preferably 0.025 inch in the direction of motion and may be in the range 0.01 to 0.05 inch. Where the motion is unidirectional the optimum spacing in the direction of movement depends on the length to width ratio of the hemicylinders and varies from 0.025 inch for hemispheres to 0.200 inch for long hemicylinders. Where the length to Width ratio is between 20:1 and 1:1 this interprotu berance spacing should be in the range 0.100 inch and 0.025 inch. The protuberances may have a root portion to give a mechanical strength. Thus as indicated in FIGURE 12 the root. may have a Width W of, for example, 0.008" and may be defined by surfaces subtending an angle or of, for example 45 where R is 0.002" and S is 0.025 inch. The interprotuberance spacing, if any, transverse to the direction of movement will affect the relationship of load to hearing area. Its selection is governed also by the consideration previously referred to in connection with the length to width ratio of the protuberances. In addition to avoid. grooving of the wood there should be protuberances aligned in the direction of movement with each of these spaces. The size of the pulp rolls formed by the rolling action provided by the profile must be maintained within reasonable limits. It is necessary with some types of grinding tools toprovidefor the removal of these rolls and it is for this rea- 1 son that spacers 51 areprovided in the structure, shown 6 in FIGURES 1 to 9 and channels 72 are provided in FIGURE 11. It the rolls are not removed they build up in size, the rolls and not the profile tends to deformthe wood structure. They wouldv act, in fact as a profile of ever increasing radius, if the rolls were allowed to get too big, particularly with reciprocating motion. This would give rise to more severe breakdown of the wood structure at ever increasing depths and lead to the production of wood fragments of ever increasing size.

The speed of the relative movement should be chosen to give good production and good pulp quality. It is preferred that where the motion is unidirectional the peripheral velocity of the grinding tool be in excess of 1000 f.p.m. Comparable speeds may be used for reciprocating motion. The type of motion aifects the quality of the pulp. Reciprocating movement is moreeffective in releasing pulp from the loosened wood structure than unidirectional motion. Also, since this release is accomplished at lower normal loads it would appear that the degradation of the wood structure is less than with unidirectional relative motion.

The loading must be. sufiicient .to provide. stresses which will give the desired pulping. but. insufiicient to degrade the Wood structure. Suitable. pressures will vary widely with the profile used and willbe lesswith reciprocating as compared with unidirectional. movement. By way of example, however, a pressure 30 p.s.i. has been found to be suitable with "the apparatus illustrated in FIG- URES 1 to 9.

The pulping tool is made of a hard material such as metal. Abrasive resistant synthetic resin may also be used.

This invention is further illustrated with the following example obtained with an apparatus as illustrated in FIGURES 1 to 9 using a tool having the profile shown in FIGURE 16.

Operating Conditions of Grinder:

Pressure, 30 p.s.i.Peripheral Speed, 4000 f.p.m. Shower Water: Rate 0.5 g.p.m. at 35 p.s.i., Temperature 140 F. Equivalent of Production Rate/ 1000 sq. in.17.2

A.D. tons/day. Pit Consistency, approximately 3.2%. Specific Energy Consumption, 63 HP. days/AD. ton. Pulp Properties:

Freeness (C.S.F. ml.) 136 Rejects, percent 5.3 Bulk, (cc/gm.) 2.45 Burst Factor 15.0 Tear Factor 41 Breaking length (M) 3600 Screen Classification: Percent R 28 17.1 28/48 19.5

/200 12.3 Pass 200 31.7

Example II illustrates the results obtained using reciprocating movement.

Example H Wood Species:

Eastern black spruce Description of Tool: Inch Radius of crown of protuberance 0.004 Height of protuberance 0.006 Spacing between protuberances 0.025 Depth of channels 0.062 Width of channels 0.25

Distance between channels (centre to centre) 0.5

Operating Conditions:

1. A pulping apparatus for the production of papermaking fibres from wood comprising a body, protuberances formed on a surface of said body, means providing relative movement between said protuberanc-es and the wood to form a pulping zone, means for applying load to one of said body and said wood, said protuberances having convex crowns which are arcuately shaped in the direction of said movement, said protuberances being adapted to create localized high intensity stresses in the subsurface of said wood to give a loosening of the wood structure and being adapted to cause the detachment of fibres from the wood, the height of said protuberances above the surface of said body being sufiicient to provide said stresses without an excessive load being borne by pulp in the spaces between the protuberances, and the height of said protuberances being insufiicient to cause burning of the wood, the spacing between the protuber ances being suthcient to give said localized high intensity stresses but insutiicient to give gross breakdown of the wood structure, said protuberances being substantially free frorn cutting surfaces and said protuberances being arranged to avoid grooving of the wood.

2. A pulping apparatus as in claim 1 in which the crowns of the protuberances when viewed in cross section in a plane perpendicular to said surface and including the direction of relative movement are substantially in the form of segments of conic sections.

3. A pulping apparatus as in claim 2 in which said body is in the form of a wheel'and in which said protuberances extend radially from the peripheral surface of said wheel, and in which said means providing relative movement causes said wheel to rotate about its axis.

4.A pulping apparatus as in claim 3 in which the crowns of said protuberances are substantially hemispherically shaped.

5. A pulping apparatus as in claim 3 in which the rowns of the protuberances have a length to width ratio of from about 20:1 to 1:1.

6; A pulping apparatus as in claim""in which said segments of conic section are substantially semicircles, the radius of the semicircular surface of the protuberances being in the range 0.002 to 0.006 inch.

7. A pulping apparatus as in claim 6 in which the height of said protuberances' above said surface of said body is in the range 0.002 to 0.010 inch.

. 8. A pulping apparatus as in claim 6 in which the interprotuberance spacing in the direction of said relative movement is from 0.025 inch to 0.100 inch.

9. A pulping apparatus as in claim 2 in which said means providing relative movement provides reciprocating movement between said protuberances and the wood.

10. A pulping apparatus as in claim 9 in which the crowns of the protuberances are hemicylinders.

11. A pulping apparatus as in claim 10 in which the segments of conic sections are substantially semicircles and the radius of the semicircular surface of the protuberances being in the range 0.002 to 0.006 inch.

7 12. A pulping apparatus as in claim 11 in which the height of said protuberances above said surface of said body is in the range of 0.002 to 0.010 inch.

13. A pulping apparatus as in claim 12 in which the interprotuberance spacing in the direction of said relative movement is from 0.01 inch to 0.05 inch.

14. A pulping apparatus as in claim 13 in which said body is a wheel which is rotated about its axis and in which the crowns of said protuberances are hemicylinders formed on the peripheral surface of said wheel and sinuously disposed so that rotation of said wheel provides relative reciprocating movement of the pattern of said protuberances with respect to the wood in a direction substantially parallel to the axis of said wheel.

15. A pulping apparatus for the production of papermaking fibres from wood comprising a body, protuberances formed on a surface of said body in a pattern, means providing relative reciprocating movement between the wood and the pattern of said protuberances to form a pulping zone, means for applying load to one of said body and said wood and means for supplying liquid to said pulping zone, said protuberances having crowns shaped in section in planes including the direction of intended relative reciprocating movement between said pattern and said wood and perpendicular to said surface substantially in the form of segments of conic sections, said protuberances being adapted to create localized high intensity stresses in the surface of said wood to give a loosening of the wood structure and adapted tocause the detachment of fibres from the wood, the height of said protuberances above the surface of said body being sufficient to provide said stresses without an excessive load being borne by pulp in the spaces between the protuberances, the spacing between the protuberances in the direction of said movement being sufficient to give localized high intensity stresses but insufiicient to give gross breakdown of the wood structure and extrusion of the wood, said protuberances being substantially free from cutting surfaces and any interprotuberance spaoes transverse to the direction of said'relative reciprocating movement being overlapped by others of the protuberances.

16. A pulping apparatus as in claim 1 in which the crowns of the protuberances are shaped substantially semicircularly in the direction of said movement.

17. A pulping apparatus for the separation of wood fibers from a wooden workpiece, including a tool, a series of spaced projections on said tool extending toward and in contact with said workpiece to provide a fiber separating zone, means providing relative movement between 9 the extremity of each of said projections, the projections and their arcuate crowns being arranged in predetermined spaced relation on said body to provide with respect to said surface laterally continuous and longitudinally spaced contact with the workpiece.

19. A pulping tool for the production of paper-making fibres from Wood comprising a body, protuberances extending from a surface of said body, said protuberances having crowns shaped in section in planes extending in one direction and perpendicular to said surface substantially as segments of conic sections, said protuberances being adapted to create localized high intensity stresses in the subsurface of said wood to give a loosening of the wood structure and adapted to cause an extraction or fibres from the wood, the height of said protuberances above the surface of said body being sufiicient to provide said stresses without an excessive load being borne by pulp in the spaces between the protuberances, the spacing between the protuberances being sufiicient to give said localized stresses but insufficient to give gross breakdown of the wood structure and extrusion of the wood, said protuberances being substantially free from cutting surfaces and said protubenances overlapping in said one direction any spaces between the protuberances in a direction transverse to said one direction, wherein the protuberances have a length to width ratio of about 20:1 to 1: 1, the crowns of the protuberances are substantially semicircular in said section and have a radius in the range 0.002 to 0.006 inch, the height of the protuberances above said surface of said body is in the range 0.002 to 0.010 inch, and the interprotuberance spacing in said one direction is from 0.025 inch to 0.100 inch.

20. A pulping tool as in claim 19 in which said body is a wheel adapted to be rotated about its axis and in which said protuberances are hemicylinders formed on the peripheral surface of said wheel and sinuously disposed so that rotation of said wheel provides relative reciprocating movement of the pattern of said protuberances with respect to the wood in a direction substantially parallel to the axis of said wheel.

21. A pulping tool for the production of paper-making fibres from wood comprising a body, protuberances extending from a surface of said body, said protuberances having crowns shaped in section in planes extending in one direction and perpendicular to said surface substantially as segments of conic sections, said protuberances being adapted to create localized high intensity stresses in the subsurface of said wood to give a loosening of the wood structure and adapted to cause an extraction of fibers from the wood, the height of said protuberances above the surface of said body being sufiicient to provide said stresses without an excessive load being borne by pulp in the spaces between the protuberances, the spacing between the protuberances being suflicient to give said localized stresses but insufficient to give gross breakdown of the wood structure and extrusion of the wood, said protuberances being substantially free from cutting surfaces and said protuberances overlapping in said one direction any spaces between the protuberances in a direction transverse to said one direction, wherein the crowns of the protuberances are substantially hemicylinders in a pattern adapted to be reciprocated, in which the radius of the semicircular surface of the protuberances provided by said hemicylinders is in the range 0.002 to 0.006 inch, the height of the protuberances above said surface of said body 10 is in the range 0.002 to 0.010 inch, and the interprotuberance spacing in the direction of reciprocation is from 0.01 to 0.05 inch.

22. A pulping apparatus for the production of papermaking fibres from wood comprising a body, protuberances formed on a surf-ace of said body, means providing relative movement between said protuberances and the wood to form a pulping zone, means for applying load to one of said body and said wood and means for supplying liquid to said pulping zone, said protuberances having crowns substantially shaped in section in planes including the direction of intended relative movement and perpendicular to said surface in the form of segments of conic sections, said protuberances being adapted to create localized high intensity stresses in the subsurface of said wood to give a loosening of the wood structure and adapted to cause a stripping out of fibres from the wood, the height of said protuberances above the surface of said body being suflicient to provide said stresses without an excessive load being borne by pulp in the spaces between the protuberances, and the height of said protuberances being insuificient to cause burning of the wood surface, the spacing between the protuberances being suificient to give said localized stresses but insufiicient to give gross breakdown of the wood structure, and said protuberances being substantially free from cutting surfaces, and said protuberances being arranged to overlap in the direction of movement any interprotuberance space transverse to the direction of movement, and means for removing pulp from said pulping zone at a sufiicient rate to prevent pulp from building up in the spaces be tween the protuberances to an extent sufiicient to remove said localized stresses, wherein said body is a wheel and in which the protuberances are formed on sectors on the periphery of said Wheel, said segments being spaced aroundthe periphery to define channels for the removal of pulp.

23. A pulping apparatus as in claim 22 in which said sectors are separately replaceable.

24. Pulping apparatus for separating fibers from wood or the like, including a body having means defining a projected profile on one surface, the surface of said profile being arcuate in contour, means to maintain a pressured cont-act of said body to the wood surface through the medium of said profile to define a pulping zone and to provide a relative movement therebetween to produce a cyclically repeated compressive action on the wood which creates a micro-fracture in its immediate subsurface the consequence of which is a reactive fiber detachment, and means in operative relation to said body for supplying fluid to said pulping zone, the means providing said relative movement between said body and the wood surface being arranged to produce a reciprocating movement.

References Elited in the file of this patent UNITED STATES PATENTS 538,697 Penfield May 7, 1895 567,187 Edison Sept. 8, 1896 1,132,258 Hall Mar. 16, 1915 1,823,627 Peterson Sept. 15, 1931 FOREIGN PATENTS 8,529 Great Britain Apr. 12, 1898 892,417 Germany Oct. 8, 1953 899,873 Germany Dec. 17, 1953 565,593 Italy June 2, 1958 

1. A PULPING APPARATUS FOR THE PRODUCTION OF PAPERMAKING FIBERS FROM WOOD COMPRISING A BODY, PROTUBERANCES FORMED ON A SURFACE OF SAID BODY, MEANS PROVIDING RELATIVE MOVEMENT BETWEEN SAID PROTUBERANCES AND THE WOOD TO FORM A PULPING ZONE, MEANS FOR APPLYING LOAD TO ONE OF SAID BODY AND SAID WOOD, SAID PROTUBERANCES HAVING CONVEX CROWNS WHICH ARE ARCUATELY SHAPED IN THE DIRECTION OF SAID MOVEMENT, SAID PROTUBERANCES BEING ADAPTED TO CREATE LOCALIZED HIGH INTENSITY STRESSES IN THE SUBSURFACE OF SAID WOOD TO GIVE A LOOSENING OF THE WOOD STRUCTURE AND BEING ADAPTED TO CAUSE THE DETACHMENT OF FIBRES FROM THE WOOD, THE HEIGHT OF SAID PROTUBERANCES ABOVE THE SURFACE OF SAID BODY BEING SUFFICIENT TO PROVIDE SAID STRESSES WITHOUT AN EXCESSIVE LOAD BEING BORNE BY PULP IN THE SPACES BETWEEN THE PROTUBERANCES, AND THE HEIGHT OF SAID PROTUBERANCES BEING INSUFFICIENT TO CAUSE BURNING OF THE WOOD, THE SPACING BETWEEN THE PORTUBERANCES BEING SUFFICIENT TO GIVE SAID LOCALIZED HIGH INTENSITY STRESSES BUT INSUFFICIENT TO GIVE GROSS BREAKDOWN OF THE WOOD STRUCTURE, SAID PROTUBERANCES BEING SUBSTANTIALLY FREE FROM CUTTING SURFACES AND SAID PROTUBERANCES BEING ARRANGED TO AVOID GROOVING OF THE WOOD. 